1. Field of the Invention
This invention relates to an anti-adhesion agent to water borne organisms, and to a paint containing such an agent for use in preventing the adhesion of water borne organisms, such as shellfish and seaweed, to such objects as the hull of ships, fishing nets, underwater structures and underwater equipment. More particularly, the invention relates to a calcium-phosphate compound carrying at least one metal or metal ion selected from the group consisting of silver, copper, zinc and nickel, and to a paint containing such a compound.
2. Description of the Prior Art
Shellfish and seaweeds such as barnacles, oysters, muscles hydrozoa, tube worm, sea moss, sea squirts, laver, green laver and others adhere to and breed on equipment and structures in constant contact with water, examples of which are facilities that are immersed in water, such as the hull of ships, fishing nets and buoys, submerged structures such as dam facilities and bridge supports, and water conduits for cooling a variety of industrial apparatus. The adhesion and propagation of such organisms on ships can lead to losses in revenue due to a reduction in traveling speed, an increase in fuel consumption, cleaning of the ship's bottom and suspension of service and so on. In underwater structures, the result can be inconvenience in terms of handling and operation. Unexpected difficulties that can occur in water conduits include blockage of the waterway and a decrease in the amount of water that can be carried.
In order to prevent such difficulties caused by the adhesion and propagation of such harmful water organisms, the practice heretofore has been to use an antifouling coating containing an oxide or an organic tin compound such as bis (tri-butyltin) oxide. However, even when such a coating is effective in preventing the adhesion of water organisms, the coating elutes into the water, and the tin compound is adsorbed by and accumulates in fish and shellfish. Copper compounds alone are inappropriate since their ions elute readily in water. Thus, such types of coatings create environmental pollution problems. Accordingly, there is a need to develop a favorable anti-adhesion agent to water borne organisms, and especially one that is not environmentally polluting.